1. Field of the Invention
The present invention relates to a method for coating a substrate as well as a precast coater. The method and precast coater allow for high solids, almost dry coating. The coating is dried on a chilled casting drum which is surrounded by external infrared heating units. The coating becomes tacky and is then peeled onto a receiving substrate.
2. Description of the Background Art
Coating methods and precast coaters are known for applying a coating onto a substrate, such as paper, paperboard, chipboard, etc. However, many problems exist with conventional coaters and coating methods. For example, all popular currently used coating processes must deal with using an appropriate amount of water such that the coating can take place while trying to avoid damage to the substrate.
It is this use of water in wetting and/or rewetting the coating or substrate which, in fact, damages the substrate and coating. The wetting and/or rewetting of the coating or substrate results in many dimensional substrate stability problems, wasted coating material, quality problems and increased process cost and complexity for the coated substrate.
One example of a conventional coating method is found in U.S. Pat. No. 2,934,467 to Bergstein. The method disclosed in this patent has not caught on in the industry because it is very slow to run (for example, 350 feet per minute).
Another drawback to this prior art method is that it is difficult to separate the coating from the casting drum on which the coating is formed. Separately applied water based adhesives must be used to get the coating to release from this casting drum. The coating is unevenly penetrated with the water based adhesive.
Another problem with existing precast coaters and coating methods is that they require relatively thick coating layer. This can cause difficulties in handling the coating and can also increase cost for the coating.
In conventional systems, it is also difficult to adequately dry the coating in a space efficient manner. There is also a need to operate the system at a fast pace. Often, excessive drying units and space for these units are needed. The extra space and many drying units required add to the costs and complexity of existing coaters.
Accordingly, a need in the art exists for a coater which can effectively apply coating to a substrate with minimal or no wetting or rewetting of the substrate and/or coating.